Ringing system for voice current repeaters



Dec. 13, 1949 i R. H. HERRICK RINGING SYSTEM FOR VOICE CURRENT REPEATERS2 she ets sheet 1 Filed Nov. 1, 1946 fillllll I. i J =2 55755 INVENTOR.ROSWELL H. HERRICK 202.501 hmu ATTORNEY Dec. 13, 1949 R. H. HERRICKRINGING SYSTEM FOR VOICE CURRENT REPEATERS' Filed NOV. 1, 1946 2Sheets-Sheet 2 INVENTOR. ROSWELL H. HE RRICK ATTORNEY 4 Patented Dec.13, 1949 B'EPE A'DERS Roswell H. Herrick, Lorain, Ohio, 'a's'sig'nor toAutomatic Electric Laboratories, Inc, Chicago, 1-11.,a corporation ofDelaware Application November 1, 1s4c,-.sem1 No, 707,100

The present invention relates in general to two-way transmission systemswhich employ separate amplifying means for transmitting signals 12Claims. (01.179 84) in each direction and is concerned morefparticuanywith new and useful improvements in. the

ringing systems of voice current repeaters.

It is an object of this invention to provide an improved ringing circuitfor use "in a standard 22-type telephone repeater.

It is a further object of this invention to'utilize this new ringingcircuit in conjunction with an improved method of frequencycharacteristic control in a standard 22-typ'e telephone repeater.

.A feature of this invention is to provide facilities in a repeatersystem of the 's'tandard 22- type telephone repeater. .for "transmittingringing signals.

Another feature of the invention is the manner in whichv it is possibleto ring, through 'on'eof the repeater channels and at the sam'e't'imedisable the complementary re eater channel thereby avoiding introductionof a singin disturbance in the complementary channel due to imperfectIih'e balance.

It is still another teatdre of the invention to provide for a pair ofleads connectedbetw'e'en the repeater and a local exchange therebyestablishing a three exchange ringing system for use in a telephonesystem employing a repeater. 'In conjunction with this local circuit,another feature of this inventionis the manner. in which the by-passcircuit is used. as part of the ringing circuit.

Another ieature of the invention is the manner energized when therepeater system is removed from theline and the connection switchedthrough .a by-pass channel'in the event of either a tube or powersupplyiailure in the amplifier. The channel switching feature utilized inconjunction With this ringing control circuit is closed in Roswell H.Herricks co-pend'ing application SerialNo 711,962 .filed November 23,I946.

A further feature of the invention is the manher in which the ringingcontrol, circuit is con- I nected to the. amplifiers at. their "inputtrian'sbest be understood by reference to the following.-

specification, taken in connection with the accompanying drawings, inwhich Figure 1 and Figure 2 when placed together as specified,illustrate a telephone repeater system having incorporated therein thefeatures of the invention as briefly outlined above.

Referring now to the drawings, Figure 1 shows a conventional 22 typerepeater, that is, there aretwo distinct one-way amplifiers arranged foruse with an ordinary two-way telephone circuit. In addition to therepeater circuit, Figure 2 shows a ringing control circuit withconductors therebetween. The system, briefly consists of a re- ,peatercircuit, a ringing control circuit and a re peater by-pass channel.

The repeater is comprised of an east and west position, an east-westchannel, and west-east channel. The line terminals are located at theeast and west positions. When the line circuit enters the east positionfrom the east lines, it will be connected to the line terminals at thewest position either through the repeater by-pass channel or theeast-west channel. The line voice current entering the west positionfrom the west line terminals will be connected to the east lineterminals either through the west-east channel or the repeater bypasschannel. The by-pass channel is comprised of contacts I and 9,,conductors 52 and 53, and contacts 22 and 24. The east-west channelconsists of contacts 8 and l0, l2 and I4, repeating coil H, balancingpads l8, hybrid system l9, east-West amplifier, hybrid system 34,balancing pad 33, repeating coil 32,. contacts 2! and 29, and con tacts23 and 25. The West-east channel is comprised of, contacts 23., 25 and21, 29,repeater coil 32,, balance pads 33 and 35, balancing network .iorthe west line 36, hybrid system 34, West east amplifier, hybrid systemI9, balance pads 18 and 20., balance network for east line 2|, repeatercoil ll, contacts 12 and i4 and contacts 8-and-l0.

The ringing control circuit consists of a two section triode tube i l,resistors 49, Ill, 14, i8, 18;, condensers 13, H13, H34, relays 'l, 2,3., 4,5, and B and. their associated contacts. The contacts of relaysSand '6 are respectively 67., 69 and 68, 8. and are located in theringing control circuit. Contacts 22,. 23., 24-, 25, H and 1, 8, 9, Hi,12 are associated respectively with relays i and 4 and are connected inthe repeater circuit at the easta-nd west positions. Relays .2 and 3,likewise, have their contacts 26, 2 1, .2-8, 29, 39, 3! and 1H, 12, 4-3,14., i5, Iii respectively positioned in the repeater circuit. Theringing control cir- 3 cult also includes a ring-in east path associatedwith a control circuit for the ring-out west, and a ring-in West pathassociated with a control circuit for the ring-out east.

The ring-in east path includes the east-west channel from the east lineterminals through the secondary winding of the input transformer 3'! atwhich point it passes through resistor 49,

conductor 62, resistor 70, and the grid of the.

lower section of tube 11, thereby causing the 4 of time that theincoming signal is effective. Relay 5 at its contacts 69 places a groundon the west repeater and thereby prevents the signal from initiating asinging disturbance within that circuit, and at its contacts 61completes a circuit from the 115 volt source to relay 2. Relay 2operates and at its contacts 2'! and 29 breaks the line connection tothe repeater channels and at its contacts 28 and 30 in the west positionapplies a completion of the path from a source of potential 93 throughrelay 5 and the lower section of tube TI. The ring-out west controlcircuit, which is utilized in combination with the ring-in east path,consists of an alternating current source of potential 96, contact 61,and relay 2. The path for a ringing signal from the west position isthrough the west-east channel to the secondary Winding of the inputtransformer 80 and continues through resistor 14 conductor 63, the uppersection of tube 11 and completes another path from the source ofpotential 93 through relay 6. The associated ring-out east controlcircuit is composed of contact 66, conductor 65, re-

lay 3, and an alternating current source of po- H tential 96.

Referring now more particularly to the operation of the system in thetransmission of signals from the east position for repeated transmissionto the west position. Assuming the repeater in the normally operatedposition relay in the east amplifier and relay 92 in the west amplifier'will be energized. The current paths of the energizing circuits areessentially the anode circuits of the tubes and more specifically forrelay 56, from the high voltage source 54 through the relay 5B, the

primary winding of the coupling transformer GE,

- the anode-cathode circuit of amplifier tube 33, the resistance at, andcontact 56 to ground. An iden- -tical path is traceable for relay 92 inthe west am- "plifier.

Relays 58 and 92, therefore, at their respective contacts 57 and 59complete a circuit in the ringing control system from the high voltagesource 99, through relays I and 4 in series, through resistor 19 inshunt of condenser 13 to ground.

Resistor 18 is of a predetermined value and effective in conjunctionwith either relays l and 4 or resistance 6! to supply the proper cathodebias to the two sections of tube l1. Relays l and 6 are thereforenormally energized and at their respective contacts 23, 25 and 8, ll!connect the east and west lines to the repeater. Additionally, on

; operating, relays i and 4 remove the short-circuit imposed on therepeater systems at their contacts 27! and 12.

Assume a ringing signal is received over the east line from a distantexchange and passes over "contacts 8 and l0, l2 and I4, throughrepeating coil IT, balance pad [8, hybrid system Hi, to the inputtransformer 31, where the signal voltage 5 is increased for use with thehigh impedance grid circuit of tube 11. The signal, unable to passfurther through the east-west amplifier circuit because of filter 4|travels over resistance 49 and conductor 62 to resistance 10 and ground.As a -result of the incoming signal received through I resistances 49and 10, the required voltage is impressed upon the lower grid of tube l1thereby The value of current through which is of an alternating currentnature. A condenser IE4 is placed in parallel with relay 5 to maintainthe relay energized for the entire period in a normal manner. feedbackcircuit impresses a large percentage of 20 cycle signal to the west linethrough contacts '23 and 25. This ringing signal is likewise transmittedto a local circuit by relay 2 at its contacts 26 and 3|. This circuit isemployed in systems where the repeater system is located in theproximity of an exchange and through a predetermined code allows theoperator at one exchange to contact either of the other two exchanges.Signals to the local line are transmitted by the east control circuitover the by-pass line when the ringing signal is applied at contacts isand [5 for a ring east signal. When the calling operator terminates theringing signal, tube Tl again becomes non-conductive and stops thecurrent supply to relay 5. Relay 5 releases and at its contact Bl breaksthe holding circuit for relay 2. Relay 2 releases and at its contacts26, 3i and 28, 3B terminates the ringing signal on the west and locallines.

When voice currents are imposed on the east line by the distantexchange, if the distance is at all large, a greatly attenuated voicecurrent enters the repeating coil ll of the telephone repeater.

In lines of varied constructon, by means of key 168, it is possible toinsert the conventional resistor balance pads l8 and 20 into the circuitwhenever an imperfect balance exists over the requisite frequency range,thereby introducing a line loss which minimizes line discontinuities andpermits overall balance. The voice current thereupon passes through ahybrid system I9, to the input transformer 3'1 of the east-westamplifier system, the input potentiometer gain control 38, amplifiertube 39, output transformer 16, filter 4], to hybrid system 34 at thewest position, half of the energy being lost in the balancing networkand the other half being transmitted through the balance pad system 33,the repeating coil 32 and over the west line via contacts 21, 29 and 23,25.

The voice current value entering the amplifier tube 39 is controlled bythe input potentiometer 38. The feedback connection from the platepasses through a condenser 82 and resistor 43 to a set of resistances 44shunted by condenser 45 and to ground. Assuming a low voice frequency istransmitted to the amplifier, the tube will amplify Being a lowfrequency, the

the potential across the input potentiometer 38 and resistances 44. Thispotential being approximately out of phase with the input due to thetube characteristics, will be of a gain reducing nature and of acomparatively large value. With a voice current of higher frequency,however, a smaller amount of feedback will occur and cause greateramplification. The negative feedback is,

therefore, a function of the input frequency, the

gain reducing value being proportionally smaller with frequencyincrease. In view of the fact that telephone attenuation is such thatthe input to thereceiver normally decreases with frequency increase,this negative feedback method of control is extremely practical; Thevalue of resistance required for different systems is a variable factorand likewise the rising frequency characteristic desired is dependententirely upon the nected in the ringing control circuit in sucha mannerthat if anode current of either channel amplifier falls below theoperating value, the relayassociated with. the failing systemwilldeenesgize, and thereupon break the circuits .for relays l and 4which in turn rernovethe repeaters tronx the line at theirassooiated'contacts 8, Wanda,

25 and connect the line terminals tethe by-1138155 channel at theircontacts 1., il-and Z2, 24;. J-f-relay 59 deenergizes, it will light supervisory lalnp 94 at its contact 55. Relay '92, ;at its contact 56-will 'iilgewise light-lamp 434; if the anode circuit offi-ts-associatedamplifier fails in any manner.

Voice currents initiated on the west lines will be transmitted hytherepeater through its westeast channel or toy-pass channel in-a similarmanner to that signal transmitted through the eastwestchannel as.previously described. The ringi-ng signal in tiated on the westconductor passes over the west-east channel to the input trans; {formerof the west-east amplifier. The signal then passes through resistance M,conductor 63, to resistor {it which with resistor [is effectiveas avoltage divider. A voltage of predetermined value isiimpressed upon thegrid of the -second section o f-tube i! as aresult of. theincoming-signal received through resistors 14 and. 18 andtherebycnengizes tube 11. Relay 6 energizes on 'the increased averageanode currentfiow from source oi-potential 9 3 and at its contacts 66completes a path from alternating currentsOurce-SB through relay 3 andatits contactstbplaces a ground on the east amplifier circuit. Relay}energizes and atits cont-acts T3 and I5 transmits a ring signal on theeast line and at its contacts T2 and Mfbreaks the line connection to the.re-

posters and at its contacts H and 16 transmits a signal over theJoy-pass channel tofthe local .line circuit. It will be noted that the,ring-in east and ring-in westpaths are grounded respectively 'by theoperation of relay 6 and relay 5 thereby averting. secondary lineringing eifects caused 'by imperfect line-balance.

ihe supervisory 'Itest key 100 when operated in "the downw'ard.lpos'i'tion removes ground from the anode'ircuit of tube 39 at itsconta'c'tJ-B and insert resistance 48 in the anode cathode Circuit.

"Th-c 112. drop across-the resistance 48 places-a high negativepotential on "the grid whereupon the anode current decreases and relay'50 de'e'nergi'z' es. Th-ebbj eat of "thisk'y' is't'o provide a simpleans "ec'on omlen 'reray a' 'a ifiubetes't ro'r the-ampune r. The keywhen operated in the upward cosinen ma es asiniil-ar. test on thewestern- 'pl1'fie'l'. When either relay d'ee'neigi'ZeS they "Will inturn lo're'ak the circuits "forrela'ys l "and 4 and insert equivalentresistance 6| in the cathode jcireuit of tube Tl. At their contacts H'and 12,.re lays land 4 place a short circuit on the amplifiers which onreoperaition precludes a s'ingingdisturbance from entering 'theline'beeause o f the tem while the. testing operation is bemgconsummated.

Relays 1'2. and 3 accomplish. a similar method of singing :precl-usivewhen they insert resistances 9,1 and 98. across the repeater systems attheir respective contacts ml and Hill-during the ringing periods.

will henoted that the input signal to the ringing control circuit isreceived from the output connection of the amplifier transformers. Inthis manner the hybrid system balance is maintained and the signalpotential is properly increased for use with the triode tube withoutthee/need of a second transformer the arrangement.

Terminals are located in the cathode circults of tubes 39and 82 as anaid to maintenance work and the grid; value of the amplifier tuhe may bereadily. determined. by inserting a voltmeter between tenminal Fix andground.

-A conventional :power supply. unit is used in combination with the-voicerepeaten The power supply unit is operated on a 115 volt, -60circuit and includes a .power transformer with various an "outgoingline, an -amplifier "connected therea plifier and fsaid grid,"a secondresistor, a

taps and a SE3 GT tube which with. the assoelated ci-rcuits is efiectiveto supply the desired 250; voltsou-rce, 23'6v1oltsource and the 6.3 voltsource. 7 p p 1tv is to glee understood that various modifications rnayfhe madein the-form of-this invention above described without.departingf-rom thespirit Of the invention as cited in the appended claims.

What is claimediS; 1 In a transmission system, an amplifier, a incomingand an ou-tgdingll'ine connectedtheremanagi control e ircuit connectedtosaidlines including a vacuum tube normally nonconduetive, an incomingsignal, amplifying .means 'in said amplifier ior amplifying. said."incoming signal, said tube, rendered conductive said amplified signalon said incoming. line, :a source of signal current, means fortransmitting. an outgoing sig- "nal from said 'source over saidoutgoingf line, .a relay "responsive .to said tube -being renderedconductive by. said 'incoming signal "to operate said means ltotransmit'said outgoing signaland to disconnect said amplifier froin.saidioutg'oing line.

2. n claim as 'ciaimeain claim -1 in which there is third line. and inwhich; o eration or "said means also connects saidthird line to saidsource,

said out'go'ing signa'l,'thereby transmitted over *said outgoing andsaid third lines, a second-relay operated Thy said ampliher'tDneposition to conheel; said outgoingfline to said amplifier and inanother position "to disconnect said outgoing Lli'ne rromisaiu amplifierand "to "connect said outgoing line to said third line, said meansefiective to transmit 'a's'igna-l from saidjsourc'etofsaid outgoing andsaid third lines when said second relay is in either"ofsaidpositions.

3'. In a transmission system, an incoming line,

fbe'tw'een, a ringing;eircuit connected "to "said lines including-a'vacuumtube having'a cathode andja g' riia'relayeonnected tosaidcathode, a'resistor, aifirst c'ireuit jforfc'onneeting said resistorbetween second circuit for con ecting said second resistor between saidgrid and ground, means including said "first circuit, "said firstresistor, said second circuit and "said second I resistor. res onsive tothe receipt. of a signal over said incoming line for am lving. a.potential Jto said ,grid to render said 'tiibe conductive saidrelayrespons ive to-saidltube becoming-conductive to thereby operate,and

extre amount or unbalance {in the-hybridsysvs meansY-for transmittin anr oute ing signalover said outgoing line responsive to the operation ofsaid relay.

4. In a transmission system, a line circuit over which voice currentsmay be transmitted in either direction, one amplifier responsive tovoice currents from one direction having an output circuit connection tosaid line circuit, another amplifier responsive to voice currents fromthe other direction having an output connection to said line circuit,and a ringing control circuit connected to said line circuit, saidcontrol circuit including a first relay, a means operated by a signaltransmitted over the line from one of said directions to energize saidfirst relay, a source of signal current, a second relay, meanscontrolled by said first relay for operating said second relay, meansresponsive to the operation of said second relay for disconnecting theoutput circuit of said one amplifier from said line circuit and fortransmitting a signal over said line circuit from said source of signalcurrent in said one direction, a third relay, said means also responsiveto a signal transmitted over said line in said other direction toenergize said third relay, a fourth relay, means controlled by saidthird relay for operating said fourth relay, means responsive to theoperation of said fourth relay for disconnecting the output circuit ofsaid other amplifier from said line circuit and for transmitting asignal over said line circuit from said source in said other direction,thereby causing said ringing signals in either of said directions toby-pass said amplifiers.

5. In a transmission system, a pair of lines, a two way voice currentrepeater including a pair of amplifiers connecting said lines, a ringingcontrol circuit connected to said repeater, including a two sectionvacuum tube, one section rendered conductive only on receipt of anincoming signal from one of said lines, the second section of saidvacuum tube rendered conductive only on receipt of a second incomingsignal from the other of said lines, a sourceof signal current, a relayoperative to transmit a signal from said source over said other lineindependent of said amplifiers, a second relay operative to transmit asignal from said source over said one line independent of saidamplifiers, a first means responsive to said first section of said tubebeing rendered conductive to operate said first relay, and a secondmeans responsive to said second section of said tube being renderedconductive to operate said second relay.

6. In a transmission system, an incoming line and an outgoing line, afirst voice current channel connected to said incoming and said outgoingline, a first amplifier in said channel having an input transformer, asecond voice current channel connected to said incoming and saidoutgoing lines, a second amplifier in said second channel having aninput transformer, a ringing circuit connected to said first channel,said second channel, said first amplifier input transformer and saidsecond amplifier input transformer, said ringing circuit including avacuum tube having one section comprised of a grid, an anode, and acathode, and a second section comprised of a grid, an anode, and acathode, a first resistor connected in series with said first amplifierinput transformer and the grid of said first section of said tube, asecond resistor connected between the grid of said first section of saidtube and ground, said first resistor and said second resistor effectiveto apply a potential to said first section of said tube on receipt of asignal from said incoming line through said first channel and said firstamplifier input transformer to render said first section of said tubeconductive, a relay, a condenser in shunt of said relay, a source ofsignal current, means connected to said outgoing line for transmitting asignal from said source over said outgoing line, said relay responsiveto said first section of said vacuum tube becoming conductive to operatesaid means, a third resistor connected in series with said secondamplifier input transformer and said grid of said second section of saidtube, a fourth resistor connected between said second grid and ground,said third resistor and said fourth resistor effective on receipt of asignal from said outgoing line through said second channel and saidsecond amplifier input transformer to render said second section of saidtube conductive, a second relay, a second condenser connected in shuntof said second relay, a second means connected to said incoming line fortransmitting a signal from said source over said incoming line, saidsecond relay responsive to said second section of said vacuum tubebecoming conductive to operate said second means.

7. In a transmission system, a pair of lines, a two way voice currentrepeater, including a pair of amplifiers, connecting said lines, a firstrelay and a second relay connected in series and operative to removesaid amplifiers from said line circuit, a third relay in and responsiveto one of said amplifiers, a fourth relay in and responsive to the otherof said amplifiers, said third and fourth relays operative to twopositions, a ringing control circuit connected to said lines having atwo section tube including a pair of cathodes,

a resistance, a second resistance, circuit means connecting said secondresistance between ground and said cathodes to maintain the grid bias ofsaid tube constant regardless of anode current value, means responsiveto the operation of said third and fourth relays to one of saidpositions for connecting said first and second relays to said cathodes,means responsive to the operation of said third and fourth relays to theother of said positions for disconnecting said first and second relaysfrom said cathodes and for connecting said first resistance to saidcathodes, said first resistance thereby effective to prevent possibledamage to said tube when said first and second relays are disconnectedfrom said source.

8. In a transmission system, a bidirectional line circuit, a first voicecurrent channel having input and output terminals connected to saidline, an amplifier in said channel responsive to signals from onedirection, a second voice current channel having input and outputterminals connected to said line, an amplifier in said second channelresponsive to signals from the other direction, a ringing controlcircuit connected to said line circuit including a two section vacuumtube, means for rendering one section of said tube conductive on receiptof a signal from said one direction on said input terminals of saidfirst channel, a relay controlled by said one section of said tube, asource of ringing current, a first means connected to control saidoutput terminals of said first channel controlled by said relay fortransmitting from said source a signal in said other direction over saidline, means for rendering the second section of said tube conductive onreceipt of a signal from said other direction on said input terminals ofsaid second. channel, a second relay controlled by said second sectionof said tube, a second means connected to control said output terminalsof said second channel for transmitting a signal from said source insaid one direction controlled by said second relay, said relays alsooperated to disconnect said channels from said line circuit.

9. A system as claimed in claim 5 in which there is an input transformerhaving secondary connections in said amplifier, said secondaryconnections being connected to said amplifier and also to said onesection of said tube, thereby increasing the potential of said firstincoming signal for energization of said tube and maintaining 1:,

a balance system in said repeater.

10. In a transmission system, a pair of lines, a two way voice currentrepeater including amplifiers connecting said lines, a by-pass circuitfor connecting said lines independent of said repeater, a thermionictube in one of said amplifiers, a relay in the plate circuit of saidtube responsive to a fall of current in said circuit to disconnect saidrepeater from said lines and connect the by-pass circuit between saidlines, a ring control plifiers connecting said lines, a by-pass circuitfor connecting said lines independent of said repeater, means in one ofsaid amplifiers operative to disconnect said repeater from said linesand connect the by-pass circuit between said lines, a ring controlcircuit connected to said lines, a relay, a vacuum tube in said controlcircuit responsive to a ringing signal over one of said lines foroperating said relay, a second relay operated by said first relay fordisconnecting said repeater from the lines, transmitting a ringingsignal over the other line, and connecting said other line to theby-pass circuit.

12. In a system as claimed in claim 11, means responsive to theoperation of said first relay for balancing said lines.

ROSWELL H. HERRICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

